One of the required functions of an engine electronic control unit (ECU) is, for example, to prevent the deterioration of engine performance and exhaust emissions by estimating the over-time degradation of parts inside related systems and correcting the estimated over-time degradation. For this reason, as a method for estimating the over-time degradation of parts, a system has been realized where the ECU stores the running condition of the engine/vehicle in an internal memory and conducts the required estimation with a given algorithm using this data. It can be expected that this type of function will be expanded even more as regulations on exhaust emissions become stricter in the future. In this manner, in conventional ECUs for vehicle or engine control, a system configuration is employed where, in addition to initialization data being stored, various types of data obtained in response to the running of the vehicle are accumulated, and control of respective parts is appropriately executed using this accumulated data.
Consequently, when such a system is employed and the ECU fails due to whatever trouble, it is necessary to first retrieve the target data inside the failed ECU with some means such as a dedicated tool and once again store the data in a new ECU with which the failed ECU is to be replaced, in order for the data that had been stored up until that point to be continuously used. However, when the portion inside the ECU for conducting communication with this tool fails, the target data can no longer be retrieved.
As technology that solves this problem, JP-A-6-19532 discloses a data backup system where plural sequencers that control equipment are connected via a transmission path. The data backup system includes a backup sequencer and command transmitting means that transmits a write command to the backup sequencer. The backup sequencer is connected to each of the sequencers via the transmission path, constantly backs up/stores backup target data of each of the sequencers, and transmits to, and writes in, the corresponding sequencers the backed up/stored data on the basis of the write command from the command transmitting means.
However, this prior art requires a special tool because it is configured to constantly back up/store the required data in the backup sequencer, and has the problem that the configuration becomes complicated and necessarily expensive.
It is an object of the present invention to provide an improved vehicular data backup method that can solve the aforementioned problem in the prior art.